Apparatus and method and computer program product for handling flash physical-resource sets

ABSTRACT

The invention introduces an apparatus for handling flash physical-resource sets, at least including a random access memory (RAM), a processing unit and an address conversion circuit. The RAM includes multiple segments of temporary space and each segment thereof stores variables associated with a specific flash physical-resource set. The processing unit accesses user data of a flash physical-resource set when executing program code of a Flash Translation Layer (FTL). The address conversion circuit receives a memory address issued from the FTL, converts the memory address into a relative address of one segment of temporary space associated with the flash physical-resource set and outputs the relative address to the RAM for accessing a variable of the associated segment of temporary space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Patent Application of and claims the benefit ofpriority to U.S. patent application Ser. No. 16/732,944, filed on Jan.2, 2020, which claims the benefit of priority to U.S. ProvisionalApplication Ser. No. 62/864,569, filed on Jun. 21, 2019; and PatentApplication No. 201910925890.X, filed in China on Sep. 27, 2019; theentirety of which is incorporated herein by reference for all purposes.

BACKGROUND

The disclosure generally relates to storage devices and, moreparticularly, to apparatus and method and computer program product forhandling flash physical-resource sets.

Flash memory devices typically include NOR flash devices and NAND flashdevices. NOR flash devices are random access—a host accessing a NORflash device can provide the device any address on its address pins andimmediately retrieve data stored in that address on the device's datapins. NAND flash devices, on the other hand, are not random access butserial access. It is not possible for NOR to access any random addressin the way described above. Instead, a central processing unit (CPU) hasto write into the device a sequence of bytes which identifies both thetype of command requested (e.g. read, write, erase, etc.) and theaddress to be used for that command. The address identifies a page (thesmallest chunk of flash memory that can be written in a singleoperation) or a block (the smallest chunk of flash memory that can beerased in a single operation), and not a single byte or word.

In the current flash specification, physical resources of a flash devicebeing shared by all applications may lead to a block of an applicationfrom accessing a physical resource of the flash device when anotherapplication occupies the same one, therefore, the overall systemperformance is degraded. The flash specification of next-generation,such as Non-Volatile Memory Express (NVMe) 1.4, separates flashphysical-resources into multiple sets and each set includes a portion ofchannels and Logical Unit Numbers (LUNs). Each of different applicationscan only perform operations, such as reads, writes, erases, etc., to onepermitted set of physical resources, so as to improve the systemperformance by reducing the probability of cross-blocks. It is requiredto re-design firmware of a flash controller to support the new features.However, poor-designed firmware may result in difficult maintenance ofprogram code, and even worse, occurrences of unexpected errors inexecutions. Thus, it is desirable to have an apparatus, a method and acomputer program product for handling flash physical-resource sets, soas to address the aforementioned problems.

SUMMARY

In an aspect of the invention, an embodiment introduces an apparatus forhandling flash physical-resource sets, at least including a randomaccess memory (RAM), a processing unit and an address conversioncircuit. The RAM includes multiple segments of temporary space and eachsegment thereof stores variables associated with a specific flashphysical-resource set. The processing unit accesses user data of a flashphysical-resource set when executing program code of a Flash TranslationLayer (FTL). The address conversion circuit receives a memory addressissued from the FTL, converts the memory address into a relative addressof one segment of temporary space associated with the flashphysical-resource set and outputs the relative address to the RAM foraccessing a variable of the associated segment of temporary space.

In another aspect of the invention, an embodiment introduces a methodfor handling flash physical-resource sets, performed by a processingunit when loading and executing program code of an FTL, at leastincluding: during a performance of an operation, after writing a numbercorresponding to a physical-resource set into a set-selection registerof an address conversion circuit, sending a memory address for avariable value to be read or written into the address conversioncircuit, thereby enabling the address conversion circuit to convert thememory address into a relative address corresponding to allocated spacefor the physical-resource set and output the relative address to a RAM;and reading the variable value from the relative address of the RAM, orwriting the variable value into the relative address of the RAM.

In still another aspect of the invention, an embodiment introduces anon-transitory computer program product for handling flashphysical-resource sets when executed by a processing unit, includingprogram code of an FTL to: during a performance of an operation, afterwriting a number corresponding to a physical-resource set into aset-selection register of an address conversion circuit, send a memoryaddress for a variable value to be read or written into the addressconversion circuit, thereby enabling the address conversion circuit toconvert the memory address into a relative address corresponding toallocated space for the physical-resource set and output the relativeaddress to a RAM; and read the variable value from the relative addressof the RAM, or writing the variable value into the relative address ofthe RAM.

Both the foregoing general description and the following detaileddescription are examples and explanatory only, and are not restrictiveof the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the system architecture of a flash memory device according toan embodiment of the invention.

FIG. 2 is a schematic diagram illustrating Logical Unit Numbers (LUNs)connecting to a flash interface.

FIG. 3 is a schematic diagram illustrating associations between commandqueues and Flash Translation Layers (FTLs).

FIGS. 4 and 5 are block diagrams for Random Access Memories (RAMs) andaddress conversion circuits according to embodiments of the invention.

FIG. 6 is a flowchart illustrating a method for processing dataaccording to an embodiment of the invention.

DETAILED DESCRIPTION

Reference is made in detail to embodiments of the invention, which areillustrated in the accompanying drawings. The same reference numbers maybe used throughout the drawings to refer to the same or like parts,components, or operations.

The present invention will be described with respect to particularembodiments and with reference to certain drawings, but the invention isnot limited thereto and is only limited by the claims. It will befurther understood that the terms “comprises,” “comprising,” “includes”and/or “including,” when used herein, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Use of ordinal terms such as “first”, “second”, “third”, etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having the same name (but for use of the ordinalterm) to distinguish the claim elements.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent.” etc.)

Refer to FIG. 1. The electronic apparatus 10 includes a host 100 and astorage device 230. The host 100 mainly includes a central processingunit (CPU) 110 and a Random Access Memory (RAM) 120. The electronicapparatus 10 may be, for example, practiced in a Personal Computer (PC),a laptop PC, a notebook, a mobile phone, a digital camera, a digitalrecorder, or other consumer electronic products. Specified regions ofthe RAM 120 may be allocated for data buffers, queues, or others. Aspecified region of the RAM 120 may be allocated for a data buffer.

The storage device 230 may include a processing unit 233 and datastorage media 234, and be optionally equipped with a RAM 231 forimproving the performance of the storage device 230. The processing unit233 may receive commands from the CPU 110 through a host interface (I/F)232 and instruct a flash controller 235 to perform data reads, datawrites, block erases, or others, accordingly. The host I/F 232 may becompatible with or support a communications protocol, such as UniversalFlash Storage (UFS), Non-Volatile Memory Express (NVMe), UniversalSerial Bus (USB), Advanced Technology Attachment (ATA), Serial AdvancedTechnology Attachment (SATA), Peripheral Component Interconnect Express(PCI-E), etc., and their extensions. Any of the CPU 110 and theprocessing unit 233 may be implemented in numerous ways, such as withgeneral-purpose hardware (e.g., a single processor, multiple processorsor graphics processing units capable of parallel computations, orothers) that is programmed using firmware or software instructions toperform the functions recited herein. The processing unit 233 furtherincludes a memory controller 236 for controlling operations of the RAM231, thereby enabling the processing unit 233 to store necessary data inexecution, such as variables, data tables, data abstracts, or others, inthe RAM 231.

The data storage media 234 may be composed of multiple Logical UnitNumbers (LUNs) 239. A flash controller 235 may communicate with the datastorage media 234 via the flash I/F 237, and specifically, the flash I/F237 may be compatible with or support a Double Data Rate (DDR) protocol,such as Open NAND Flash Interface (ONFI), DDR toggle, or others. Theflash controller 235 of the storage device 230 writes user data into adesignated address (a destination address) of the data storage media 234and reads user data from a designated address (a source address) thereofthrough the flash I/F 237. The flash I/F 237 may use several electronicsignals including a data line, a clock signal line and control signallines for coordinating command and data transfer between the flashcontroller 235 and the data storage media 234. The data line may be usedto transfer commands, addresses, read data and data to be programmed;and the control signal lines may be used to transfer control signals,such as Chip Enable (CE), Address Latch Enable (ALE), Command LatchEnable (CLE), Write Enable (WE), etc. The processing unit 233 and theflash controller 235 may be implemented in separate chips or integratedinto a single chip.

The LUNs 239 provide huge storage space typically in Gigabytes, or evenTerabytes, for storing a wide range of user data, such ashigh-resolution images, video files, etc. The LUNs 239 include controlcircuits and memory arrays containing memory cells, such as Triple LevelCells (TLCs) or Quad-Level Cells (QLCs).

The RAM 231 may be used to buffer user data, which is instructed by theCPU 110, that is to be programmed into the LUN 239 and has been readfrom the LUN 239 but hasn't been clocked out to the CPU 110, andLogical-Physical mapping (L2P) tables for fast lookup. The RAM 231 mayadditionally store necessary data in execution of software and firmwareinstructions, such as variables, data tables, data abstracts, or others.The RAM 231 may include a Static Random Access Memory (SRAM), a DynamicRandom Access Memory (DRAM), or both.

Refer to FIG. 2. The flash I/F 237 may include four I/O channels(hereinafter referred to as channels) CH#0 to CH#3 each is connected tothree LUNs, for example, the channel CH#0 is connected to the LUNs239#0, 239#4, 239#8 and 239#12. One die may include one LUN 239 or more,and each LUN 239 may be controlled by a designated CE signal. Thus, theflash controller 235 may drive the flash I/F 237 to issue one of the CEsignals CE#0 to CE#3 to activate the LUNs 239#0 to 239#3, the LUNs 239#4to 239#7, the LUNs 239#8 to 239#11, or the LUNs 239#12 to 239#15, andread data from or program data into the activated LUNs in parallel.

In the new flash standard, the channels and LUNs 239 can be separatedinto multiple physical-resource sets (hereinafter referred to as setsfor brevity) and a portion of channels and LUNs 239 are included in eachset. Multiple sets operate independently and are managed separately fromeach other. For example, the physical resources may be divided intothree sets: The set Set#0 includes the channels CH#0 and CH#1, and LUNs239#0˜1, 239#4˜5, 239#8˜9 and 239#12˜13; the set Set#1 includes thechannel CH#2 and LUNs 239#2, 239#6, 239#10 and 239#14; and the set Set#2includes the channel CH#2 and LUNs 239#3, 239#7, 239#11 and 239#15.

After configuring the channels and the LUNs 239 as multiple sets, theCPU 110 allocates space of the RAM 120 for multiple queue sets and eachqueue set is associated with one physical-resource set individually.Refer to FIG. 3. For example, the set Set#0 is associated with aSubmission (SQ) 310#0 and a Completion Queue (CQ) 330#0, the set Set#1is associated with a SQ 310#1 and a CQ 330#1 and the set Set#2 isassociated with a SQ 310#2 and a CQ 330#2. Each SQ is used to store hostcommands from the CPU 110, which are read and executed by the storagedevice 230. Each CQ is used to store Completion Elements (CEs) that aregenerated by the storage device 230 to show execution results, forexample, successes and fails, after the host commands are executed. TheCPU 110 may read the CEs to know the execution results of the hostcommands. Each of the SQs and the CQs contains a collection of entries.Each entry of the SQ may store one host command, specifically one I/Ocommand, such as a read command, a write command, etc. The entries inthe collection are kept in order preferably. The principle operations onthe collection are the addition of entities to the rear terminalposition (for example, the position pointed by a pointer SQT or CQT),known as enqueue, and removal of entities from the front terminalposition (for example, the position pointed by a pointer SQH or CQH),known as dequeue. That is, the first command added to the SQ will be thefirst one to be removed. Thus, the CPU 110 may output multiple I/Ocommands that can be read and executed by the processing unit 233 and/orflash controller 235 of the storage device 230. After that, theprocessing unit 233 and/or flash controller 235 of the storage device230 feedback executions results to make the CPU 110 know the executionresults of the I/O commands.

For the configurations supporting multiple sets, the processing unit 233may activate and execute multiple Firmware Translation Layers (FTLs)individually associated with one set. Refer to FIG. 3. For example, theset Set#0 is associated with the FTL 350#0, the set Set#1 is associatedwith the FTL 350#1 and the set Set#2 is associated with the FTL 350#2.The FTL 350 is mainly responsible for mapping Logical Block Addresses(LBAs) come from the host 100 to physical addresses of the LUNs 239(so-called logical-to-physical mapping). All LBAs representing thelogical units visible to and managed by the host-side file system aremapped to a physical location (channel ID, block ID, page ID and sectorID) of the LUNs 139. The physical location for an LBA might bedynamically changed in the wear leveling, and other backgroundmanagement algorithms, such as garbage collection (GC), data moving,etc., to improve the endurance of memory cells of the LUNs 239. Althoughthe following takes the FTL 350#0 as an example, those artisans canapply the relevant techniques to the other FTLs with relevantmodifications. In some embodiments, the processing unit 233 whenexecuting the FTL 350#0 reads (or fetches) the I/O command that isearliest arrived for the set Set#0 from the SQ 310#0, and drives theflash I/F 237 to manipulate the LUNs 239 via the flash controller 235according to the parameters (such as an LBA, etc.) of the I/O command,so as to complete an execution of the I/O command. After a completion ofthe operations, the processing unit 233 when executing the FTL 350#0writes a CE into the CQ 330#0. Lastly, the CPU 110 may read the CE todetermine the execution result of the I/O command. In alternativeembodiments, for example, in the background mode, the processing unit233 when executing the FTL 350#0 may actively drive the flash I/F 237 tomanipulate the LUNs 239 via the flash controller 235, so as to completea specific background operation, such as a wear leveling, a GC, a datamoving process, or others.

However, the above design has obvious drawbacks. The processing unit 233when executing multiple FTLs 350 for accessing to multiple sets not onlyconsumes hardware and software resource but also times spending in FTLloadings and switches between the FTLs 350. To address the drawbacks,the invention discloses a method for processing data, in which a singleFTL 350 is executed and managed, multiple sets of variables that arerequired by the single FTL 350 are set, and each variable set isassociated with one physical-resource set. When accessing to the nextset, the FTL 350 preserves/updates variables associated with the currentset, and then, obtains variables associated with the next set.Therefore, the FTL 350 can use the variables associated with the nextset for accessing to the next set. That thus, it can achieve theobjective of managing/accessing to multiple sets by a single FTL 350.

To achieve the above objectives, variables associated with the set haveto be determined first, and the remaining are variables irrelevant fromthe set. Variables associated with the set (hereinafter may refer to asvariables for brevity) include but not limit to, for example, an activeblock number, an active page pointer, a spare block amount for eachplane, a wear-leveling count for each block and an erase count for eachblock. Examples of the variable declaration are expressed as follows:

-   -   Private garActiveFBlock;    -   Private garActiveFPage;    -   Private garSpareFBlock[C_MaxPlane];    -   Private garWearLevelingCnt[C_MaxBlock];    -   Private garBlockEraseCnt[C_MaxBlock];        The parameter C_MaxPlane indicates a total amount of data planes        of a specific set. The parameter C_MaxBlock indicates a total        amount of blocks of a specific set. The parameter        garActiveFBlock indicates an active block number of a specific        set. The parameter garSpareFBlock[] indicates a total amount of        spare blocks for each plane of a specific set. The parameter        garWearLevelingCnt[] indicates a wear-leveling counter for each        block of a specific set. The parameter garBlockEraseCnt[]        indicates an erase counter for each block of a specific set.        Since the variables are associated with a particular set, the        variables are preferably declared as private variables. But, it        is also feasible to declare the variables as public variables.

Next, storage addresses of the variables are determined. The presentinvention allocates multiple segments of temporary space of the RAM 231and each segment of the temporary space stores the variables associatedwith one set. Refer to FIG. 4. For example, the RAM 231 includes amemory unit 2311, in which the variables associated with sets Set#0,Set#1 and Set#2 are stored in temporary space of address ranges0xA000˜0xAFFF, 0xB000˜0xBFFF and 0xC000˜0xCFFF, respectively.

Lastly, an address conversion circuit 500 is provided in the storagedevice 230 for converting a memory address that is advised by the FTL350 to retrieve a variable associated with a specific set into a memoryaddress of specific temporary space. The address conversion circuit 500is preferably provided in a memory controller 236. In some embodiments,the address conversion circuit 500 may be practiced in the architectureas shown in FIG. 4. The address conversion circuit 500 may use theequation (1) to convert a memory address that an FTL attempts toretrieve into a relative address Addr* of temporary space correspondingto a specific set:

Addr*=Addr+SET*OFFSET

The parameter Addr indicates a memory address that an FTL attempts to bewritten into or read from. The parameter SET indicates a set numberstored in a set-selection register 510. The parameter OFFSET indicates avalue stored in an offset register 530, indicating a total length ofmemory space that is allocated for each set. The processing unit 233when executing the FTL 350 sets the value of the set-selection register510 to a number of the corresponding set. For example, before accessingto the RAM 231, the FTL in execution stores “0”, “1”or “2” in theset-selection register 510. A default value may be stored in the offsetregister 530 before the storage device 230 leaves from a manufacturingfactory or when a boot process of the storage device 230 is executed. Amultiplier 550 coupled to the set-selection register 510, the offsetregister 530 and the adder 570 times the value of the set-selectionregister 510 by the value of the offset register 530 and outputs thecalculation result to an adder 570. The adder 570 coupled to theprocessing unit 233 receives the memory address Addr that the FTL 350attempts to retrieve from the processing unit 233, and pluses thecalculation result output from the multiplier 550 to the memory addressAddr to generate a relative address Addr*. The memory controller 236outputs the relative address Addr* to the RAM 231.

The RAM 231 includes a command-and-address decoder 2317 coupled to thememory controller 236. The command-and-address decoder 2317 receives acommand CMD issued by the FTL 350 from the memory controller 236,receives the relative address Addr* from the memory controller 236 andinterprets the received command CMD and the relative address Addr*. TheRAM 231 further includes a read-write control circuit 2313 and a databuffer 2315. The read-write control circuit 2313 is coupled to thememory unit 2311 and the command-and-address decoder 2317 and the databuffer 2315 is coupled to the read-write control circuit 2313 and theprocessing unit 233. The read-write control circuit 2313 receives a readcommand and a read address from the command-and-address decoder 2317,reads a specified length of data from the read address (or referred toas a start address) of the memory unit 2311 and outputs the data to thedata buffer 2315, enabling the processing unit 233 when executing theFTL 350 to obtain a designated variable value DAT from the data buffer2315. In addition, the read-write control circuit 2313 receives a writecommand and a write address from the command-and-address decoder 2317,reads a designated variable value DAT that the processing unit 350 whenexecuting the FTL 350 attempts to write from the data buffer 2315, andwrites the variable value DAT into the write address of the memory unit2311.

In alternative embodiments, the address conversion circuit 500 may bepractice in the architecture as shown in FIG. 5. Refer to FIG. 5. Theset-selectin register 610 is similar with the set-selection register 510as shown in FIG. 4 to store a number of the corresponding set by the FTL350 in execution. The address conversion circuit 500 further includesmultiple address registers and each address register stores a startaddress of the variables corresponding to one set. For example, thefirst to third address registers 631, 633 and 635 store startingaddresses “0xA0000”, “0xB0000” and “0xC0000” for the variables of thesets Set#0, Set#0 and Set#2, respectively. Default values may be storedin the first to third address registers 631, 633 and 635 before thestorage device 230 leaves from a manufacturing factory or when a bootprocess of the storage device 230 is executed. The address conversioncircuit 500 further includes a multiplexer (MUX) 650 coupled to thefirst to third address registers 631, 633 and 635, the set-selectionregister 610 and an adder 670 for connecting one of the first to thirdaddress registers 631, 633 and 635 to the adder 670 according to acontrol signal Ctrl corresponding to the value of the set-selectionregister 610. For example, when the value of the set-selection register610 is “0”, the MUX 650 connects the first address register 631 to theadder 670. When the value of the set-selection register 610 is “1”, theMUX 650 connects the second address register 633 to the adder 670, andso on. The adder 670 coupled to the processing unit 233 receives thememory address Addr that the FTL 350 attempts to retrieve from theprocessing unit 233 and pluses the starting address output from the MUX650 to the memory address Addr to generate a relative address Addr*. Thememory controller 236 outputs the relative address Addr* to the RAM 231.

In the address conversion circuit 500 as shown in either FIG. 4 or FIG.5, for example, the memory controller 236 outputs the relative address“0xA010” to the RAM 231 when the FTL 350 stores “0” in the set-selectionregister 510 or 610 and sends the memory address “0x0010”. The memorycontroller 236 outputs the relative address “0xB010” to the RAM 231 whenthe FTL 350 stores “1” in the set-selection register 510 or 610 andsends the memory address “0x0010”. The memory controller 236 outputs therelative address “0xC010” to the RAM 231 when the FTL 350 stores “2” inthe set-selection register 510 or 610 and sends the memory address“0x0010”.

With reflection of the address conversion circuit 500 as shown in FIG. 4or FIG. 5, FIG. 6 illustrates an embodiment of a method for processingdata, which is performed by the processing unit 233 when loading andexecuting program code of the FTL 350.

Step S610: The processing unit 233 obtains a target I/O command from oneof SQs individually associated with one set. For example, the SQ 310#0is associated with the set Set#0, the SQ 310#1 is associated with theset Set#1 and the SQ 310#2 is associated with the set Set#2. Theprocessing unit 233 when executing the FTL 350 reads one I/O command ormore associated with the set Set#0 from the SQ 310#0 as the target I/Ocommand or commands, reads one I/O command or more associated with theset Set#1 from the SQ 310#1 as the target I/O command or commands, orreads one I/O command or more associated with the set Set#2 from the SQ310#2 as the target I/O command or commands. The FTL 350 preferablyreads the I/O commands of different sets from the 310#0, 310#1 and 310#2in the round-robin manner. Or, the FTL 350 determines the reading orderand the quantities of I/O commands from the SQ 310#0, 310#1 and 310#2according to weight settings. The FTL 350, for example, cyclically readsone, two and three I/O commands associated with sets Set#0, Set#1 andSet#2 from the SQs 310#0, 310#1 and 310#2 as the target I/O commands,respectively.

Step S630: The processing unit 233 writes the set number correspondinginto the read SQ in the memory controller 236. For example, theprocessing unit 233 when executing the FTL 350 reads the target I/Ocommand associated with the set Set#0 from the SQ 310#0, and then,writes “0” into the set-selection register 510 or 610 of the memorycontroller 236.

Step S650: The processing unit 233 outputs a command and a memoryaddress Addr to the memory controller 236 to access a target variable.Since the processing unit 233 writes “0” into the set-selection register510 or 610 of the memory controller 236, the memory controller 236converts the memory address Addr into the relative address Addr*,thereby enabling the processing unit 233 to access the target variableassociated with the set Set#0 that is stored at the relative addressAddr* of the RAM 231 via the memory controller 236. In other words, theFTL 350 may read the variable value associated with the set Set#0 fromthe relative address Addr* of the RAM 231 or write the variable valueassociated with the set Set#0 into the relative address Addr* of the RAM231.

Step S670: The processing unit 233 executes the target I/O commandaccording to the target variable. After obtaining the target variable,the FTL 350 can execute target I/O command or update the target variablecorrectly. For example, the processing unit when executing the FTL 350performs data reads from the LUNs 230#0˜1 or data writes into the LUNs230#4˜5 according to the variables associated with the set Set#0.

Step S690: The processing unit 233 writes an execution result of thetarget I/O command into the CQ corresponding to the read SQ. Forexample, the processing unit 233 when executing the FTL 350 writes a CEindicating an execution success into the CQ 330#0 in response tosuccessful data reads from the LUNs 239#0˜1. The CPU 110 reads the CEfrom the CQ 330#0 and knows the execution result of the I/O command ofthe SQ 310#0.

Some or all of the aforementioned embodiments of the method of theinvention may be implemented in a computer program such as a driver fora dedicated hardware of a storage device, or others. Other types ofprograms may also be suitable, as previously explained. Since theimplementation of the various embodiments of the present invention intoa computer program can be achieved by the skilled person using hisroutine skills, such an implementation will not be discussed for reasonsof brevity. The computer program implementing some or more embodimentsof the method of the present invention may be stored on a suitablecomputer-readable data carrier such as a DVD, CD-ROM, USB stick, a harddisk, which may be located in a network server accessible via a networksuch as the Internet, or any other suitable carrier.

Although the embodiment has been described as having specific elementsin FIGS. 1, 2, 4 and 5, it should be noted that additional elements maybe included to achieve better performance without departing from thespirit of the invention. Each element of FIGS. 1, 2, 4 and 5 is composedof various circuits and arranged to operably perform the aforementionedoperations. While the process flows described in FIG. 6 include a numberof operations that appear to occur in a specific order, it should beapparent that these processes can include more or fewer operations,which can be executed serially or in parallel (e.g., using parallelprocessors or a multi-threading environment).

While the invention has been described by way of example and in terms ofthe preferred embodiments, it should be understood that the invention isnot limited to the disclosed embodiments. On the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

What is claimed is:
 1. An apparatus for handling flash physical-resourcesets, comprising: a random access memory (RAM), comprising a pluralityof segments of temporary space, wherein each segment of temporary spacestores variables associated with a specific flash physical-resource set;a processing unit, coupled to the RAM, arranged to operably access userdata of a flash physical-resource set when executing program code of aFlash Translation Layer (FTL); and an address conversion circuit,coupled to the RAM, arranged to operably receive a memory address issuedfrom the FTL, convert the memory address into a relative address of onesegment of temporary space associated with the flash physical-resourceset and output the relative address to the RAM for accessing a variableof an associated segment of temporary space, wherein the addressconversion circuit comprises: a set-selection register; a plurality ofaddress registers, wherein each address register is arranged to operablystore a start address of the RAM that is associated with a specificflash physical-resource set; an adder; and a multiplexer, coupled to theset-selection register, the address registers and the adder, arranged tooperably connect one of the address registers to the adder according toa control signal corresponding to a value of the set-selection register,wherein the adder is arranged to operably plus the start address of aconnected address register to the memory address to generate therelative address, and output the relative address to the RAM.
 2. Theapparatus of claim 1, wherein the FTL sets a number corresponding to anassociated flash physical-resource set to the set-selection registerbefore accessing to the RAM.
 3. The apparatus of claim 1, wherein eachflash physical-resource set comprises a portion of channels and aportion of Logical Unit Numbers (LUNs).
 4. The apparatus of claim 1,comprising: a flash interface, coupled to the processing unit, whereinthe FTL drives the flash interface to access user data of the flashphysical-resource set according to an accessed variable.
 5. Theapparatus of claim 4, wherein the user data is accessed during aperformance of an operation being associated with an I/O command readfrom a submission queue.
 6. The apparatus of claim 4, wherein the userdata is accessed during a performance of an operation being a backgroundoperation irrelevant from a host.
 7. The apparatus of claim 6, whereinthe background operation is garbage collection (GC).
 8. A method forhandling flash physical-resource sets, performed by a processing unitwhen loading and executing program code of a flash translation layer(FTL), comprising: during a performance of an operation, after writing anumber corresponding to a physical-resource set into a set-selectionregister of an address conversion circuit, sending a memory address fora variable value to be read or written into the address conversioncircuit, thereby enabling the address conversion circuit to convert thememory address into a relative address corresponding to allocated spacefor the physical-resource set and output the relative address to arandom access memory (RAM); and reading the variable value from therelative address of the RAM, or writing the variable value into therelative address of the RAM, wherein the address conversion circuitcomprises: the set-selection register, arranged to operably store thenumber associated with the physical-resource set; a plurality of addressregisters, wherein each address register is arranged to operably store astart address of the RAM that is associated with a specificphysical-resource set; an adder; and a multiplexer, coupled to theset-selection register, the address registers and the adder, arranged tooperably connect one of the address registers to the adder according toa control signal corresponding to the number associated with thephysical-resource set, wherein the adder is arranged to operably plusthe start address of a connected address register to the memory addressto generate the relative address, and output the relative address to theRAM.
 9. The method of claim 8, wherein the operation is associated withan I/O command read from a submission queue.
 10. The method of claim 8,wherein the operation is a background operation irrelevant from a host.11. The method of claim 8, wherein the RAM comprises a plurality ofsegments of temporary space and each segment of temporary space storesvariables associated with a specific flash physical-resource set. 12.The method of claim 8, comprising: during the performance of theoperation, driving a flash interface to access user data of thephysical-resource set according to the variable value.
 13. The method ofclaim 8, wherein each flash physical-resource set comprises a portion ofchannels and a portion of Logical Unit Numbers (LUNs).
 14. Anon-transitory computer program product for handling flashphysical-resource sets when executed by a processing unit, thenon-transitory computer program product comprising program code of aflash translation layer (FTL) to: during a performance of an operation,after writing a number corresponding to a physical-resource set into aset-selection register of an address conversion circuit, send a memoryaddress for a variable value to be read or written into the addressconversion circuit, thereby enabling the address conversion circuit toconvert the memory address into a relative address corresponding toallocated space for the physical-resource set and output the relativeaddress to a random access memory (RAM); and read the variable valuefrom the relative address of the RAM, or writing the variable value intothe relative address of the RAM, wherein the address conversion circuitcomprises: the set-selection register, arranged to operably store thenumber associated with the physical-resource set; a plurality of addressregisters, wherein each address register is arranged to operably store astart address of the RAM that is associated with a specificphysical-resource set; an adder; and a multiplexer, coupled to theset-selection register, the address registers and the adder, arranged tooperably connect one of the address registers to the adder according toa control signal corresponding to the number associated with thephysical-resource set, wherein the adder is arranged to operably plusthe start address of a connected address register to the memory addressto generate the relative address, and output the relative address to theRAM.
 15. The non-transitory computer program product of claim 14,wherein the operation is associated with an I/O command read from asubmission queue.
 16. The non-transitory computer program product ofclaim 14, wherein the operation is a background operation irrelevantfrom a host.
 17. The non-transitory computer program product of claim16, wherein the background operation is garbage collection (GC).
 18. Thenon-transitory computer program product of claim 14, wherein the RAMcomprises a plurality of segments of temporary space and each segment oftemporary space stores variables associated with a specific flashphysical-resource set.
 19. The non-transitory computer program productof claim 14, comprising program code of the FTL to: during theperformance of the operation, drive a flash interface to access userdata of the physical-resource set according to the variable value. 20.The non-transitory computer program product of claim 14, wherein eachphysical-resource set comprises a portion of channels and a portion ofLogical Unit Numbers (LUNs).